The present invention relates to an acoustical insulation laminate product and more specifically to an acoustical insulation laminate product comprising an acoustical insulation mat or absorbing material, a polyolefin face, backing, or both, and a front and back face cloth which increase the total noise reduction coefficient.
The use of fiberglass in the manufacturing of acoustical and insulation products is well known. Moreover, insulation materials comprised of fiberglass and organic fibers, including cotton, as well as synthetic or man-made fibers, formed into mats and utilizing a thermo-setting resin have been utilized for many years in the manufacturing of insulation and acoustical products. For example, U.S. Pat. No. 2,689,199 teaches the use of thermoplastic polymers and refractory fibers of glass in the manufacture of a non-woven porous flexible fabric and U.S. Pat. No. 2,695,855 teaches the use of cotton, rayon, nylon or glass fibers with an appropriate resin for a thermal or acoustical insulation material. And, U.S. Pat. No. 4,888,235 teaches a non-woven fibrous product comprising a blended matrix of glass fibers and synthetic fibers having a conductive material of powdered aluminum, copper or carbon black and a thermo-setting resin dispersed in the matrix. However, a number of these insulation products which contain glass fibers and synthetic fibers are generally brittle and are easily broken or cracked when subjected to excessive flexing during installation or use. Moreover, these acoustic insulation products generally absorb high frequencies well but do not absorb low frequencies as well.
There are generally three types of fiberglass which may be used to make the acoustical insulation. The first two types are known as rotary and flame-attenuated fiberglass which are generally formed of about 5 microns or less diameter glass fiber strands, but may exceed 5 microns depending on the application. The third type of fiberglass is typically known as continuous strand or textile fiberglass and generally has a diameter of greater than 5 microns. Comparing the three types, the first two products are typically more expensive to produce, historically have better sound absorption characteristics, but cause more irritation to human skin, are more respirable due to their smaller diameter and therefore are more of a health hazard. And, although the smaller diameter allows for greater density which corresponds to its ability to absorb sound, the smaller diameter results in less durability. On the other hand, the textile fiberglass is typically stronger, more durable, and less hazardous to humans.
Although the fiberglass acoustical insulation and most other sound absorbers typically work well for higher frequency sounds above about 2500 Hz, the lower range frequencies are more difficult to absorb. Frequencies less than about 2500 Hz often pass through known fiberglass acoustical insulations which is highly undesirable in, for instance, an automobile.
Non-porous polyfilms have been used with acoustical absorbing materials in order to absorb limited specific frequencies rather than a wider range of frequencies. However, this is not useful in situations where an enclosure is bombarded by a wide range of acoustical frequencies. Moreover, the polyfilm, which typically absorbs low frequency sounds, dramatically decreases the ability of the sound absorption material to absorb high frequency sounds.
In view of the deficiencies in known acoustical laminates, it is apparent that an acoustical laminate is needed which effectively absorbs both high range frequencies and low range frequencies, is cost effective, lightweight, durable, and stronger than known acoustical absorbing materials.
It is an object of the present invention to provide an improved acoustical insulation laminate comprising an acoustical insulation mat and a polyolefin film having equal or greater performance than existing absorbing material at a lighter weight.
It is a further object of the present invention to provide an acoustical insulation laminate with a wide range of frequency absorption.
It is yet an even further object to provide an acoustical insulation for automobiles, which are lighter in weight than other acoustic insulations, thereby improving gas mileage and reducing automobile operating expense.
It is still a further object to provide a porous polyfilm in combination with and which enhances known acoustical sound absorbers such as fiberglass, cotton, synthetic, cotton-synthetic blends other acoustical absorbers whether man-made or natural in order to provide an equal or greater range of sound absorption.
It is also an object of the present invention to provide a highly effective sound absorbing laminate using recycled raw materials that are economical to produce.
It is still an even further object of the present invention to provide a polyolefin film having a total flow-through opening of at least 0.25 percent of the surface area of the film, and preferably between 0.25 percent and 50 percent of the surface area of the film.
Even one further object of the present invention is to provide a process for forming the acoustical laminate having a porous polyolefin layer.
More particularly, the acoustical insulation laminate of the present invention includes an insulation mat or absorbing material and a porous polyfilm or polyolefin film. One example of an absorbing material that may be used in the present invention is a fiberglass fibrous material with nylon and a thermo-setting resin co-binder. An example of such a fiberglass mat is set forth in U.S. Pat. No. 5,883,020 issued to Bargo et al. and is incorporated herein by reference.
The instant invention further includes at least one layer of porous polyolefin film or polyfilm affixed to the acoustical insulation mat in order to absorb the lower range frequencies that the acoustical insulation mat typically does not absorb well. The polyfilm typically acts as a barrier to high frequency sounds, however, the porous nature of the polyfilm of the instant invention allows the polyfilm to act as an absorber for low frequency sound, yet allows a wide range of higher frequency sounds to pass through to the absorbing material wherein prior polyfilm laminates have failed. The polyfilm may be a thermo-setting plastic so that the polyfilm thermally bonds to the acoustical insulation mat. Alternatively, the polyfilm may be applied to the acoustical insulation mat with the use of resins, co-polymers, polyesters and other thermoplastic materials. The polyfilm is preferably comprised of a polyolefin, particularly a polypropylene or polyethylene and should be positioned between the sound source and the acoustical insulation mat so that the film resonates against the absorbing material to destroy acoustical energy of the low frequency sound. The polyfilm preferably has a plurality of spaced acoustical flow-through openings allowing high frequency sounds to pass therethrough and be absorbed by the acoustical insulation mat. The surface area of the at least one acoustical flow-through opening may be between 0.25 percent and 50.0 percent. Prior to molding, the acoustical flow-through openings may be circular, square, or any other pre-selected geometric shape including slits. And, upon molding, the polyfilm comprises multiple random shaped apertures having various shapes, sizes, and areas permitting the film to absorb low frequency sounds and permitting high frequency sounds to pass through and be absorbed by the acoustical absorbing material. In operation the polyfilm absorbs low frequency sounds by resonating and destroying acoustical energy while reflecting some high frequency sounds. Other high frequency range sounds passing through the acoustical flow-through openings are absorbed by the acoustical insulation mat. The polyfilm may be used with known rotary, flame-attenuated, or textile fiberglass absorbers as well as other acoustical absorbers in order to enhance their ability to absorb a wide frequency range of sounds.
Finally the acoustical insulation laminate may include a face cloth extending over the film. The face cloth helps retain the laminate together and provides an aesthetically pleasing appearance. The face cloth also affects the amount of distortion of the polyfilm apertures and therefore the performance of the polyfilm.
All of the above outlined objectives are to be understood as exemplary only and many more objectives of the invention may be gleaned from the disclosure herein. Therefore, no limiting interpretation of the objectives noted is to be understood without further reading of the entire specification, claims, and drawings included herewith.